1. Field of the Invention
This invention relates generally to RFID (Radio Frequency Identification) systems and more specifically relates to a method and system of using active tags for providing a reliable and secure RFID system.
2. Description of the Prior Art
RFID tags and readers have recently begun to enter the mass market. FIG. 1 illustrates a typical prior art RFID system, in which RFID reader 100 uses a first frequency to read RFID tags 117, 118, 119 and 120 in a large area that is populated with signposts 101–116. A second frequency is used to send commands from signpost 101–116 to the RFID tags 117, 118, 119 and 120. FIG. 2 shows a typical prior art RFID tag including low-frequency receiver 200, timer 201, microprocessor 202, UHF transmitter 203, and power source 204. Low-frequency receiver 200 receives commands from signposts 101–116 and UHF transmitter 203 sends data to RFID reader 100. A shortcoming of this prior art system is that the signposts cannot have overlapped zones and need careful cell planning, and the system needs at least two frequencies to operate and can encounter throughput problems when the RFID tag population increases in the large read zone of the RFID reader.
While this prior art system may be suitable to the early deployment of RFID applications, it is desirable to provide an improved system for reliability and throughput purposes in which a RFID reader network includes multiple readers using active RFID tags.